Slowly but surely the unlimited data plan for mobile phones is slipping away.

First it was AT&T, which announced last year that it was getting rid of its unlimited data plan to ensure mobile data overeaters didn't gobble up a disproportionate share of network resources. T-Mobile followed with a plan that it still calls "unlimited," but actually throttles usage after users hit a certain threshold. And soon Verizon Wireless will also be saying bah-bye to unlimited data.

For most consumers, who use well below the thresholds that carriers charge for overages, the switch to a tiered offering probably won't affect them. But for heavy data users and for people concerned that their usage will increase in the future, the elimination of unlimited data plans is causing a great deal of hand-wringing and angst about the future.

In this week's Ask Maggie, I advise a heavy-data-using Verizon Wireless subscriber to re-up his contract pronto to keep his good deal before it ends.

Also in this week's Ask Maggie column, I dispel the rumor that AT&T is not allowing existing smartphone customers to keep their unlimited data service when they upgrade to "4G" HSPA+
phones. And finally, I answer a question about whether a dual-mode LTE/WiMax chip will come on the market soon.

The end of unlimited data

Dear Maggie,
I'm ready to upgrade from my original Droid, but I've been patiently waiting for the Motorola Droid Bionic. Now that Verizon is planning to end unlimited data plans, should I stop the waiting game and lock myself in for a two-year contract with the Verizon Droid Charge by Samsung or the HTC Thunderbolt? Or should I keep waiting? I use about 3GB to 4GB of data per month.

Thanks,
Dustin

Dear Dustin,
Holy mackerel, you use a lot of data my friend! You are one of those heavy data users that all the operators complain about. AT&T said a year ago when it moved to its tiered pricing plan that 98 percent of its customers use less than 2GB of data per month. I don't know for sure what the stat is today, but I doubt very much that your usage fits into the average user's profile.

So what should you do? Given your usage, it makes sense for you to stick with an unlimited plan. The big question is how can you do that? You are correct about Verizon's intentions to eliminate the unlimited plan on its network. The company is moving toward a tiered pricing model. Several executives have confirmed this publicly. This week, Verizon Chief Financial Officer Fran Shammo said at the Barclays Capital investor conference that the carrier will move to the tiered offering this summer. Shammo also confirmed that as Verizon moves to a tiered offering, the company would stop offering the unlimited data plan.

"I'm not going to go into exactly what we are going to launch in the summertime, but we actually will be going to tiered pricing. The unlimited pricing will be taken off the table," he said, according to a transcript from the event.

Neither Motorola nor Verizon is being specific about a launch date for the Droid Bionic. But Motorola told The Wall Street Journal that it will be released this summer. And as I pointed out, Verizon also said that its unlimited plans are going away this summer.

The company hasn't said whether it will "grandfather" existing customers who already have an unlimited plan when the new policy takes effect so that when people upgrade to a new phone they get to keep their unlimited plans. This is the policy that AT&T has adopted.

So if I were you, I wouldn't wait around for the Droid Bionic. If you really want to keep your unlimited data plan, you should probably choose one of the 4G Android phones from Verizon already on the market. Bonnie Cha said in her review that she really likes the Samsung Droid Charge.

The reason I say get a phone now is that Verizon must honor whatever contract you have agreed to when it changes its plans. So if you lock into the unlimited plan now, you should be able to keep it for at least two years until your contract ends.

After that, it's anyone's guess what will happen with data pricing. AT&T was the first carrier to move to tiered pricing last year. T-Mobile USA says it has an unlimited plan, but the company recently began throttling back speeds after users hit a pre-set data cap. (Besides in two years, T-Mobile will likely be owned by AT&T, which plans to buy T-Mobile for $39 billion.) After Verizon gets rid of its unlimited data plans, Sprint Nextel will be the only major wireless carrier left that offers true unlimited data. But even Sprint has said that it hasn't ruled out moving to a tiered offering.

Anyway, my advice to you is to get locked in to the unlimited plan while you can. It may be your last chance.

Keeping your AT&T unlimited data plan

Dear Maggie,
I am confused as to why AT&T wireless is making their customers who have been "grandfathered" in with unlimited 3G data plans change to a tiered data plan if they want to upgrade to a so-called 4G phone. I have chatted with both an AT&T representative and a BestBuy salesman online about upgrading to the Motorola Atrix. But both reps told me that I could not keep my existing unlimited data plan with AT&T, because they said that only people upgrading to 3G wireless services are grandfathered into the unlimited data plans. What's really annoying about this is that Atrix doesn't even support real 4G. It's an HSPA+ phone and not an LTE or WiMax device. Why is there this double standard?

Thanks,
Mileskw

Dear Mileskw,
I've got great news for you. The reps you spoke with are wrong. I checked with Mark Siegel, the spokesman for AT&T, and he told me that "if you are a smartphone customer on the unlimited plan and want to keep it, you can --even if you choose another smartphone." I asked him to double-check that this included the new HSPA+ phones, such at the Motorola Atrix and the Samsung Infuse, and he said "yes."

So you should be good to go. If the sales rep continues to tell you that this is not the policy, I'd suggest asking for a supervisor, who should know the correct policy.

Dual-mode LTE/WiMax chips coming

Hello Maggie,
I would like to know if you are aware of a chipmaker who will be putting out a dual radio in a phone or laptop that can access WiMaX and LTE. From what I understand both standards are similar. I read an article about Beecem Chip that can support LTE and WiMaX.

Thanks,
Ronald

Dear Ronald
Several companies, including Beceem/Broadcom, Intel, and Sequans are working on dual-mode LTE and WiMax chips. And those chips should be ready in the market very soon. WiMax and LTE are based on the OFDMA (orthogonal frequency-division multiple access) technology, so getting the two to co-exist in the same chip shouldn't be too difficult.

That said, it's unclear whether device makers will see any compelling reason to offer devices with such chips built into them. LTE has the clear lead in terms of technology of choice for mobile broadband in the U.S. and abroad. Verizon Wireless has already launched its LTE network and AT&T is about to launch its network this summer. Vodafone, the largest wireless operator in the world, is also planning to use LTE for its next-generation wireless network. And most other carriers around the world are moving toward LTE.

Because it will be so widely deployed, LTE is likely to take advantage of economies of scale and therefore gear to build those networks, as well as the consumer devices themselves, will be cheaper than devices made for WiMax networks.

That said, WiMax is not expected to go away. Sprint and Clearwire in the U.S. are building a nationwide WiMax network for mobile data users. And in other parts of the world, WiMax is used to offer fixed wireless connections.

But there are indications that Sprint and Clearwire may be considering adding LTE to their networks.

If this happens, the dual-mode WiMax/LTE chips could be used by networking equipment vendors to help make it easier for operators to switch between the two technologies. And there may be a need for some consumer devices to have both functionalities. This way the user wouldn't have to care or think about whether they are using a WiMax or LTE device on which network.

Even with dual-mode chips, it doesn't necessarily mean that a consumer using a smartphone from Verizon Wireless would be able to use that same device to roam onto Sprint's WiMax network. In fact, Verizon LTE devices used today likely won't roam seamlessly onto European carrier networks using LTE, because different frequencies are used to offer the service in different regions.

The more pressing issue for device makers and wireless providers is to establish a standard that will allow interoperability among various next-generation wireless networks.